Curable compositions containing epoxy and polyamide resins are known in the art. For example, European Patent Application Publication No. 0 157 478 describes adhesive compositions prepared by mixing solid particles of polyamide resins with solid particles of epoxy resins. If desired, the composition also contains a polymeric binder. Prior to application as an adhesive, the polyamide and epoxy composition is preferably dispersed in a non-solvent.
Hastings et al., U.S. Pat. No. 3,945,964, describes stable aqueous emulsions of epoxy resins containing, as emulsifying agents, ethylene oxide propylene oxide block polymers of specified formulae. Curing agents described as useful with the epoxy resin emulsion include polyamides.
Aelony et al., U.S. Pat. No. 2,899,397, describes mixed aqueous emulsions of polyamide and epoxy resins prepared by mixing a solution of epoxy resinous material with a solution of polymeric polyamides, combining the two solutions in the presence of an aqueous medium containing a water soluble organic carboxylic acid and agitating the combined solutions to produce an emulsion.
Wittcoff and Renfrew U.S. Pat. No. 2,811,495 discloses mixtures of suspensoids of polyamide resins and complex epoxide resins, but there is no suggestion of the stability enhancing, water soluble, dipolar chemical moieties of the present invention.
One problem with many of the prior art epoxy/polyamide resin compositions, however, is the rapid reactivity of the mixed resins, producing in a relatively short amount of time an infusible, insoluble composition. Where such compositions are intended for use as laminating agents, adhesives, potting and casting resins, and the like, this brief reaction time requires that the resin mixture be prepared at point of use and in relatively small quantities. Attempts have been made to lengthen the shelf life of these compositions, however, such attempts have met with little success. In addition, relatively large amounts of volatile organic solvents used in these processes (i.e. toluene, isopropanol, methylethyl ketone) are flammable and environmentally undesirable.
New and/or better curable epoxy and polyamide resin compositions, particularly compositions having a longer and more stable shelf life, are needed. The present invention is directed to these important ends.